Blow molding machine

ABSTRACT

A blow molding machine provided with a blow head to hold molding sand therein, at least one passage connected to an upper portion of the blow head at one end thereof and connected to a pressurized air supply source at the other end so as to apply compressed air to the molding sand held in the blow head, for blowing and charging the molding sand from the blow head into a mold space that is located adjacent the blow head and then compacting the charged molding sand to produce a sand mold. The blow molding machine includes at least one chamber disposed on an inner surface of an external wall of the blow head at a middle portion of the blow head, the chamber having an inner surface facing the molding sand held in the blow head, at least part of the inner surface having a plurality of apertures to allow air to pass through them, and a pressurized air supply source connected to the chamber to supply compressed air into the chamber and into the molding sand to fluidize it.

FIELD OF THE INVENTION

[0001] This invention relates to an improvement of a blow molding machine.

DESCRIPTION OF THE PRIOR ART

[0002] A prior-art blow molding machine is disclosed in Japanese Patent Kokai (JP, A) 6-277,800, which was laid open to the public on Oct. 4, 1994. That blow molding machine has a blow head, a plurality of juxtaposed air passages with blow-off ports being connected to the blow head, for adjusting the pressure and the flow rate of air to be supplied to the blow head, and an air supply source connected to the take-in port of each passage. In this molding machine, compressed air is introduced into the blow head to blow molding sand from the blow head into a pair of mated frames, and this charged molding sand is then compressed in the frames.

[0003] In such a molding machine, when a blow head has a large capacity for molding sand to be charged into frames that also have a large capacity, compressed air introduced into the upper part of the blow head to blow the molding sand from the blow head into the frames cannot move the molding sand with a sufficient speed. This results in poorly compacting the molding sand.

SUMMARY OF THE INVENTION

[0004] This invention has been conceived in view of the above drawback. It aims to provide an improved blow molding machine that can cause molding sand to flow in a blow head at a sufficient speed even if a large amount of molding sand is charged from the blow head into the frames that define a mold space.

[0005] To this end, in one aspect of the present invention, the blow head of the blow molding machine of this invention includes at least one chamber. This chamber is disposed on the inner surface of the external wall of the blow head at the middle portion of the blow head. The chamber has a perforated inner surface which faces the molding sand held in the blow head. A pressurized air supply source is connected to the chamber. When pressurized air is supplied from the source or another air supply source to the molding sand, which is held in the blow head, to blow it into the mold space, pressurized air is also supplied from the source (that is connected to the chamber) into the chamber. The air from the source passes through the apertures formed in the inner surface of the chamber and then passes through the molding sand at the middle portion of the blow head. Thus the molding sand is fluidized and has sufficient speed. It is then well charged into the mold space.

[0006] The molding machine of the above aspect may include a plurality of juxtaposed passages connected to the upper part of the blow head. Each of these passages is selectively opened and closed to adjust the pressure and flow rate of the air to be supplied to the blow head to blow the molding sand into the mold space.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a sectional view of an embodiment of a blow molding machine of the present invention.

[0008]FIG. 2 is a sectional view in an enlarged scale of the blow head of the molding machine of FIG. 1.

[0009]FIG. 3 is a cross-sectional view along line III—III in FIG. 2.

[0010]FIG. 4 is a cross-sectional view along line IV—IV in FIG. 2.

[0011]FIG. 5 is a cross-sectional view similar to FIG. 4, to show an alternative blow head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012]FIG. 1 show a cross-sectional view of an embodiment of the blow molding machine of the present invention. The molding machine includes a pair of frames 2, 4 that can contact each other. A vertical match plate 6 is supported between the frames 4, 4 in any known manner. The match plate 6 holds a large pattern part 6 a and a small pattern part 6 b on one of its surfaces and also large and small pattern parts 6 a, 6 b on the other surface. The frames 2, 4 have blow-in ports 8, 10 respectively. Pressing plates 12, 14 are inserted into the frames 2, 4 respectively. The pressing plates 12, 14 are respectively pushed inward by cylinders 16, 18. The frame 2, match plate 6, and pressing plate 12 define a mold space 2 a, while the frame 4, match plate 6, and pressing plate 14 define a mold space 4 a.

[0013] In reference to FIGS. 1-4, it is seen that the blow molding machine includes a blow head 20. The blow head 20 is comprised of an upper portion 22, a middle portion 24, and a lower portion 26. The upper portion 22 is a cylindrical tube, as shown in FIG. 3, and has a flange 22 a at the bottom, as shown in FIG. 2. The middle portion 24 is a square tube, as shown in FIG. 4, and has a flange 24 a at the top and a flange 24 b at the bottom, as shown in FIG. 2. The lower portion 26 is a square tube at its upper portion and has a flange 26 a at the top. The top portion 22 and the middle portion 24 are secured to each other through the flanges 22 a, 24 a, while the middle portion 24 and the lower portion 26 are secured to each other through the flanges 24 b, 26 a.

[0014] As shown in FIGS. 1 and 2, the upper portion 22 has a sand-feeding mouth 28 and a gate 30 at the top. As shown in FIG. 1, a pipe 32 at one end is connected to the upper portion 22 at a location near the top thereof. This pipe 32 at the other end is connected to a passage assembly 34 which has a plurality of passages 34 a. Each passage 34 a has a valve 36, and all the valves 36 are connected to a pressurized air supply source 40 through pipes 38. The valves 36 are selectively opened or closed in any known manner to adjust the pressure and speed of an air flow that is supplied from the air source 40 through the pipe 32. The passage assembly 34 acts as means to adjust the pressure and speed of the air flow or air flows which are introduced into the blow head 20 to blow molding sand S from the blow head 20 into the mold spaces 2 a, 4 a.

[0015] As is clear from FIGS. 2 and 3, a cylindrical tube 42, which is integrally made from four plates 42 a, 42 b, 42 c, and 42 d, is secured to the inner surfaces of the upper and middle portions 22, 24. The cylindrical tube 42 is shaped as a conical frustum at the upper portion 22 and as a square tube at the middle portion 24. As is clear from FIGS. 2 and 4, the plate 42 a, an upper small plate 44 a, a lower small plate 44 b, two side small plates 44 c, 44 d, and the external wall of the middle portion 24 define a chamber 48 on the inner surface of the external wall. A plurality of small apertures 52 are formed in at least part of an inner wall 44 e of the chamber 48. These small apertures are small enough so that they do not allow the molding sand S to come into the chamber 48. Similarly, the plate 42 c, an upper small plate 46 a, a lower small plate 46 b, two side small plates 46 c, 46 d, and the external wall of the middle portion 24 define another chamber 50 on the inner surface of the external wall. A plurality of small apertures 52 are also formed in an inner wall 46 e of the chamber 50. The chamber 48 is connected to the pressurized air supply source 40 (FIG. 1) through a connecting pipe 54 and a valve 56. Alternatively, the chamber 48 may be connected to another pressurized air supply source (not shown). A distribution pipe 58 connects the connecting pipe 54 to the chamber 50. Thus, when the valve 56 is opened, air is introduced from the air supply source into the chambers 48, 50, as shown by arrows.

[0016]FIG. 5 is a horizontal, cross-sectional view similar to FIG. 4 and shows an alternative embodiment of the chambers 48, 50. In the alternative embodiment, two more chambers 60, 62 are provided in addition to the chambers 48, 50. The chamber 60, 62 are defined in a manner similar to that for defining the chambers 48, 50. The four chambers 48, 50, 60, 62 are separated from each other in the embodiment shown in FIG. 5. Alternatively, these chambers may be replaced with a single, continuous, annular chamber. An annular distribution pipe 64 is connected to the pipe 54 and the chambers 48, 50, 60, 62 such that the air from the air supply source is distributed to all the chambers.

[0017] The lower portion 26 of the blow head 20 has forked pyramids 26 a, 26 b at its lower part (FIG. 1). The pyramids 26 a, 26 b have a tip or nozzle 27 a and a tip or nozzle 27 b, respectively. The blow head 20 is supported for vertical movement in any known manner such that the nozzles 27 a, 27 b are sealingly inserted into the blow-in ports 8, 10 of the frames 2, 4 (mold spaces 2 a, 4 a).

[0018] In operation, the blow head 20 is lowered so that the nozzles 27 a, 27 b are inserted into the blow-in ports 8, 10 of the mated frames 2, 4. The gate 30 is then opened, and a predetermined amount of molding sand is introduced into the blow head 20 through the mouth 28. This state is shown in FIG. 1. The valve 56 is then opened, so that pressurized air flows into the chambers 48, 50, as shown in FIG. 4 (or the chambers 48, 50, 60, 62 as shown in FIG. 5, or the single continuous chamber described above) and into the molding sand S, thereby fluidizing it. An appropriate number of the passages 34 a of the passage assembly 34 are selected. Their associated valves 36 are opened for an appropriate period, so that an air flow suitable to the amount of the molding sand S is introduced into the blow head 20.

[0019] When the air is introduced into the blow head 20, preferably, two or more air flows are used. The pressure, flow rate, and period of the air flows are adjusted or varied in accordance with the size of the space, i.e., the distances between the pressing plate 12 (or 14) and the pattern portions 6 a, 6 b. For example, an air flow is used so that the long space between the pressing plate 12 (or 14) and the small pattern portion 6 b is filled with the molding sand in a high density, and a next air flow is used so that the short space between the pressing plate 12 (or 14) and the large pattern portion 6 a is filled with the molding sand in a low density. A third air flow is used so that the top part of the mold space 2 a (or 4 a), i.e., the upper and long space between the match plate 6 and the pressing plate 12 (or 14), is filled with the molding sand in a high density.

[0020] Since the molding sand S is fluidized at the middle portion 24 of the blow head 20, it is well charged into the mold spaces 2 a, 4 a. The air flows introduced into the blow head 20 through the pipes 32 and 54 are discharged from vent holes (not shown) provided in the frames 2, 4. The molding sand blown and charged into the frames 2, 4 is then compressed by the pressing plates 12, 14 of the cylinders 16, 18. After this compression, the pressing plates 12, 14 are withdrawn from the frames 2, 4, and the blow head 20 is lifted up to withdraw the nozzles 27 a, 27 b from the blow-in ports 8, 10 of the frames. The hardened molding sand is taken out in any known manner. Thus two sand molds (drag and cope) that have no frame are produced.

[0021] If the outer surfaces of the pattern portions 6 a, 6 b are substantially flat, to obtain the same compression effect as above the pressure and the flow rate of the air flow that is used for the lower parts of the mold spaces 2 a, 4 a can be less than those of the air flow that is used for the upper parts of the mold spaces.

[0022] The foregoing embodiments are exemplary only. It is not intended that the invention be limited to them. It will be understood by one skilled in the art that any other variation and modification can be made without departing from the spirit and the scope of the invention. Thus those variations and modifications are understood to be included in the attached claims. 

What we claim is:
 1. A blow molding machine provided with a blow head to hold molding sand therein, at least one passage connected to an upper portion of the blow head at one end thereof and connected to a pressurized air supply source at the other end so as to send compressed air to the molding sand held in the blow head, for blowing and charging the molding sand from the blow head into a mold space that is located adjacent the blow head and then compacting the charged molding sand to produce a sand mold, comprising: at least one chamber disposed on an inner surface of an external wall of the blow head at a middle portion of the blow head, the chamber having an inner surface facing the molding sand held in the blow head, at least part of the inner surface having a plurality of apertures to allow air to pass through the apertures, and a pressurized air supply source connected to the at least one chamber to supply compressed air into the chamber and into the molding sand, thereby fluidizing the molding sand.
 2. The blow molding machine of claim 1 , wherein the pressurized air supply source connected to the upper portion of the blow head is the pressurized air supply source that is connected to the at least one chamber.
 3. The blow molding machine of claim 1 or 2 , comprising a plurality of juxtaposed passages connected to the upper portion of the blow head, the passages being selectively opened and closed.
 4. The blow molding machine of claim 1 , 2 , or 3, wherein the at least one chamber is at least one chamber that extends around the periphery of the inner surface of the external wall of the blow head. 